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Importance of Cation Exchanger in Purified Water System

Working and significance of the cation exchanger in purified water system during water purification.
Water is widely used and an important raw material in the processing, formulation and production of pharmaceutical products and medical devices. Purified water has unique chemical properties making it ideal to absorb, dissolve or adsorb many different compounds. Having a purified water system in pharmaceuticals is a great way to control the quality of water all through the production, storage and distribution processes.

In pharmaceuticals, purified water is also necessary for washing laboratory instruments. Therefore, incorporating a cation exchanger in purified water system ensures the purified water meet the stringent standards. The ions in water are exchanged for other ions that ensure purity.

Ion Exchanger

Raw water has suspended particles such as colloids, silt and pipework debris. It also has dissolved inorganic compounds that are the major impurities, which include magnesium and calcium salts, which cause “hardness” of water. Raw water also contains carbon dioxide that forms weak carbonic acid.

Other inorganic compounds are sodium salts, chlorides from saline interference, nitrates from fertilizers, phosphates from detergents, iron compounds from rusty iron pipes and others. A cation exchanger is ideal for eliminating these impurities from raw water to ensure purified water for pharmaceuticals.

This method of water purification works through beds of ion exchange resins that efficiently eliminate ionized species from raw water by exchanging them for OH- and H+ ions. The ion exchange resins can be described as sub 1mm porous beads that are made of extremely cross-linked unsolvable polymers with huge numbers of sturdily ionic exchange sites.

The ions in solution move into the beads that are either anionic or cationic. The cation exchanger in purified water system has strong cation resins that are generally polysulfonic acid derivatives of polystyrene cross-linked with di-vinyl benzene.

The beds of ion exchange resins are available either in cylinders or in cartridges. The cartridges or cylinders can either be removed or replaced from the site for remote regeneration or as an arrangement of vessels, tanks, pumps and valves that allow on-site regeneration of the ion exchange resins. 

Working of Cation Exchanger:

The cation exchanger resin removes positively charged ions such as magnesium and calcium by exchanging H+ ions for the heavier and more highly charged cations. Once “tired”, the cation resin is re-energized by exposing the resin to an excess of a strong acid such hydrochloric acid (HCl).

However, the very large surface area of a cation exchange resin makes it an ideal breeding area for microorganisms, which can lead to the release of soluble and fines components. Therefore, good quality resins should be used and bed volumes maintained as small as sensibly possible.

The modern cation exchanger design uses comparatively small resin beds and keeps frequent regeneration schedules to minimize the chances for microbial growth. In addition, filters should be installed after the beds to trap particles and other fines. The bacterial buildup is minimized by ensuring frequent recirculation of the water and by frequent cartridge replacement.

Therefore, with suitable choice of system design and resin pretreatment, achieve the lowest levels of cation contamination cation exchanger in the purified water system.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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